The present invention relates to an apparatus for machining an inner circumferential surface of a workpiece which defines a cylindrical bore, for instance, a cylinder bore surface of a cylinder block of an engine for automobiles, and a method of machining the inner circumferential surface using the apparatus. More specifically, the present invention relates to an apparatus for use upon boring the inner circumferential surface of the workpiece and forming microscopic recesses as oil retention portions on the inner circumferential surface in order to reduce friction on the inner circumferential surface, and relates to a method of machining the inner circumferential surface using the apparatus.
Conventionally, upon boring a cylinder bore surface of a cylinder block of an engine and forming a plurality of microscopic recesses on the cylinder bore surface, the cylinder bore surface is subjected to boring and honing and then subjected to shot blasting to form the microscopic recesses thereon. Upon shot blasting, a masking sheet with through-holes having a predetermined shape is attached to the cylinder bore surface, and then small-diameter shots, such as ceramic balls, are blasted with compressed air against the cylinder bore surface. As a result, microscopic recesses are formed on a part of the cylinder bore surface which is exposed outside through the through-holes. Subsequently, the masking sheet is taken off, and the cylinder bore surface is subjected to cleaning and honing to thereby remove protrudent portions projecting around the recesses which are formed upon shot blasting. Japanese Patent Application First Publication No. 2002-307310 describes such a masking and blasting method as explained above.